This invention relates to improved instruments of a type utilizing gyroscopes to produce a directional indication or response. The invention will be described primarily as applied to well instruments, such as surveying instruments or steering tools in which gyroscopic means are provided for indicating azimuth. It is to be understood, however, that certain aspects of the invention are also applicable to equipment usable at locations other than in a well.
In cased wells and in some other types of wells where it is not possible to utilize magnetic sensors responsive to the earth's magnetic field, gyroscopic units are employed for indicating azimuth. Difficulties are encountered, however, in assuring maintenance of an accurately reliable heading of a gyroscope during the often substantial period of time required for lowering the instrument into a well, and in preventing unwanted variations in the heading as a result of friction of the bearings of the gyroscope, slight imperfections in manufacture, and other uncontrollable factors.